I checked out Hang em High fabrics and they had 1/2 oz Polycarbonate Coated Ripstop Polyester which is 3/4 oz coated. It sounds like it would be waterproof but to what degree. The 54" wide fabric is $12.99 but considering the weight this isn't bad. From what I have read polyester tends to sag less than nylon. At this low weight I'm not sure how well it would hold up though. Does anyone have experience with this material?